/* ===================================
   BUTTON ATOM - Atomic Design Foundation
   ===================================

   Single source of truth for all button variants.
   Uses design tokens from design-tokens.css
*/

/* Base button styles */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  font-family: var(--font-family-sans);
  font-weight: var(--font-weight-medium);
  line-height: var(--line-height-tight);
  text-decoration: none;
  border: var(--border-width-1) solid transparent;
  border-radius: var(--border-radius-md);
  cursor: pointer;
  transition: all var(--duration-200) var(--easing-out);
  white-space: nowrap;
  user-select: none;
  position: relative;
}

/* Button focus styles */
.btn:focus-visible {
  outline: var(--border-width-2) solid var(--border-focus);
  outline-offset: var(--border-width-2);
}

/* Button disabled state */
.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  pointer-events: none;
}

/* ===================================
   BUTTON VARIANTS
   =================================== */

.btn-primary {
  background-color: var(--color-primary);
  color: var(--text-inverse);
  border-color: var(--color-primary);
}

.btn-primary:hover:not(:disabled) {
  background-color: var(--color-primary-hover);
  border-color: var(--color-primary-hover);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.btn-primary:active:not(:disabled) {
  transform: translateY(0);
  box-shadow: var(--shadow-xs);
}

.btn-secondary {
  background-color: var(--bg-surface);
  color: var(--text-primary);
  border-color: var(--border-default);
}

.btn-secondary:hover:not(:disabled) {
  background-color: var(--bg-surface-hover);
  border-color: var(--border-strong);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.btn-secondary:active:not(:disabled) {
  transform: translateY(0);
  box-shadow: var(--shadow-xs);
}

.btn-danger {
  background-color: transparent;
  color: var(--color-error);
  border-color: transparent;
}

.btn-danger:hover:not(:disabled) {
  background-color: var(--color-error-light);
  border-color: transparent;
}

.btn-ghost {
  background-color: transparent;
  color: var(--text-primary);
  border-color: transparent;
}

.btn-ghost:hover:not(:disabled) {
  background-color: var(--bg-surface-hover);
  border-color: var(--border-default);
}

.btn-link {
  background-color: transparent;
  color: var(--color-primary);
  border-color: transparent;
  text-decoration: underline;
  padding: 0;
  min-height: auto;
}

.btn-link:hover:not(:disabled) {
  color: var(--color-primary-hover);
  background-color: transparent;
  transform: none;
  box-shadow: none;
}

/* ===================================
   BUTTON SIZES
   =================================== */

.btn-sm {
  padding: var(--space-1_5) var(--space-3);
  font-size: var(--text-sm);
  min-height: var(--button-height-sm);
}

.btn-md {
  padding: var(--space-2) var(--space-4);
  font-size: var(--text-sm);
  min-height: var(--button-height-md);
}

.btn-lg {
  padding: var(--space-2_5) var(--space-5);
  font-size: var(--text-base);
  min-height: var(--button-height-lg);
}

/* ===================================
   BUTTON ICONS
   =================================== */

.btn-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.btn-icon svg {
  width: var(--icon-size-sm);
  height: var(--icon-size-sm);
  stroke-width: 2;
}

/* Icon-only buttons */
.btn.btn-icon {
  padding: var(--space-2);
  min-width: var(--button-height-md);
  aspect-ratio: 1;
}

/* ===================================
   BUTTON STATES
   =================================== */

.btn-loading {
  position: relative;
  color: transparent;
}

.btn-loading .btn-spinner {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: var(--icon-size-sm);
  height: var(--icon-size-sm);
  border: var(--border-width-2) solid transparent;
  border-top-color: currentColor;
  border-radius: var(--border-radius-full);
  animation: spin 1s linear infinite;
}

@keyframes spin {
  from { transform: translate(-50%, -50%) rotate(0deg); }
  to { transform: translate(-50%, -50%) rotate(360deg); }
}

/* ===================================
   BUTTON MODIFIERS
   =================================== */

.btn-full {
  width: 100%;
}

/* Button groups */
.btn-group {
  display: inline-flex;
}

.btn-group .btn {
  border-radius: 0;
  margin: 0;
}

.btn-group .btn:first-child {
  border-radius: var(--border-radius-md) 0 0 var(--border-radius-md);
}

.btn-group .btn:last-child {
  border-radius: 0 var(--border-radius-md) var(--border-radius-md) 0;
}

.btn-group .btn:not(:first-child) {
  border-left: 0;
}

/* ===================================
   RESPONSIVE ADJUSTMENTS
   =================================== */

@media (max-width: 640px) {
  .btn {
    font-size: var(--text-sm);
  }

  .btn-sm {
    padding: var(--space-1) var(--space-2_5);
    min-height: var(--space-8);
  }

  .btn-md {
    padding: var(--space-1_5) var(--space-3);
    min-height: var(--space-9);
  }

  .btn-lg {
    padding: var(--space-2) var(--space-4);
    min-height: var(--space-10);
  }
}